Automotive regenerative braking devices having energy storage assemblies employing metal springs are well known. In general such devices have been manually operated to effect vehicle braking by converting vehicle motion (kinetic energy) into resiliently stored potential energy and manually operated to effect vehicle acceleration with the stored energy. The storage assemblies employing metal springs have been unduly bulky and/or heavy. Further, the amount of braking and driving torque provided by such assemblies has not been readily controllable.
In co-pending U.S. patent application Ser. No. 944,442, filed Sept. 21, 1978 and now U.S. Pat. No. 4,246,988, applicant discloses a regenerative braking system having a control system for modulating braking and driving torques provided by a storage assembly having torsionally stressed rubber rollers. While this control system is an effective way to control braking and acceleration torques, it has the disadvantage of requiring rapid on-off control of clutches and brakes under relatively high torque loads and substantial rotational speed differences.